The introduction of digital mobile communication systems, such as the panEuropean mobile telephone system GSM, signifies a breakthrough, when the intention is to support mobile data transmission in public cellular networks. Since the GSM is entirely digital and utilizes general principles of an ISDN (Integrated Services Data Network), the GSM is inherently capable of transmitting data. For the user, the GSM does not represent a dedicated data transmission network, but an Access Network. In other words, data transmission via GSM is intended to allow an access into dedicated data networks. The current GSM recommendations specify only circuit switched data services in a cellular network. This means that a circuit switched connection is reserved for a data transmission in a mobile communication network and radio resources are kept allocated during the entire data session, even during silent periods when no communication whatsoever occurs. Because one characteristic feature of data communication is that data is sent in bursts, a circuit switched transfer is expensive for the user and wastes channel capacity in the network infrastructure. There is thus a need for connectionless (not circuit switched) packet data services in the GSM network infrastructure.
The architecture of a conventional packet data network can be considered as a single virtual network consisting of a plurality of small interconnected networks. Each terminal equipment, e.g. a computer, is connected to one of these local networks, i.e. packet nodes, capable of transmitting data packets via other nodes to a recipient. Each data packet is routed separately, i.e. the node computer searches for the address of the recipient in a packet header and forwards the data packet to the next node by using an internal routing algorithm.
There are various dedicated packet switched radio networks. It is, however, difficult to apply solutions used in such networks to already standardized (an even setup) GSM networks, without making significant modifications in the standard operation and configuration of the network and without significant economic investments. No effective solutions to provide a connectionless packet switched data transfer in a fixed network of the GSM system or a corresponding mobile communication system have been presented.